D. Solovyev

QED calculation of E1M1 and E1E2 transition probabilities in one-electron ions with arbitrary nuclear charge

The quantum electrodynamical theory of the two-photon transitions in hydrogenlike ions is presented. The emission probability for 2s1/2 → 2γ(E1) + 1s1/2 transitions is calculated and compared to the results of the previous calculations. The emission probabilities 2p1/2 → γ(E1) + γ(E2) + 1s1/2 and 2p1/2 → γ(E1) + γ(M1) + 1s1/2 are also calculated for the nuclear charge Z values 1 ≤ Z ≤ 100. This is the first calculation of the two latter probabilities. The results are given in two different gauges.

Asymmetry of the Natural Line Profile for the Hydrogen Atom.

The asymmetry of the natural line profile for transitions in hydrogenlike atoms is evaluated within a QED framework. For the Lyman- alpha 1s-2p absorption transition in neutral hydrogen this asymmetry results in an additional energy shift of 2.929 856 Hz. For the 2s(1/2)-2p(3/2) transition it amounts to -1.512 674 Hz. As a new feature this correction turns out to be process dependent. The quoted numbers refer to the Compton-scattering process.

Influence of external electric fields on multi-photon transitions between the 2s, 2p and 1s levels for hydrogen and antihydrogen atoms and hydrogen-like ions

One- and two-photon transitions in the hydrogen atom are analytically evaluated in the absence and in the presence of an external electric field. The emission probabilities in the external electric field are different for the hydrogen (H) and anti-hydrogen () atoms due to the existence of contributions that are linear in the electric field. The magnitude of these contributions is evaluated within the nonrelativistic limit. The three-photon E1E1E1 2p-1s transition probability is also evaluated and possible applications of the results are discussed.

Theoretical Study of the Accuracy Limits of Optical Resonance Frequency Measurements

The principal limits for the accuracy of the resonance frequency measurements set by the asymmetry of the natural resonance line shape are studied and applied to the recent accurate frequency measurements in the two-photon 1s-2s resonance and in the one-photon 1s-2p resonance in a hydrogen atom. This limit for 1s-2s resonance is found to be approximately 10(-5) Hz compared to the accuracy achieved in experiment +/-46 Hz. In the case of a deuterium atom the limit is essentially larger: 10(-2) Hz. For 1s-2p resonance the accuracy limit is 0.17 MHz while the uncertainty of the recent frequency measurement is about 6 MHz.

Extension of the sum rule for the transition rates between multiplets to the multiphoton case

Abstract. The sum rule for the transition rates between the components of two multiplets, known for the one-photon transitions, is extended to the multiphoton transitions in hydrogen and hydrogen-like ions. As an example the transitions 3p–2p, 4p–3p and 4d–3d are considered. The numerical results are compared with previous calculations.

Two-photon decays of highly excited states in hydrogen

The relativistic and nonrelativistic approaches for the calculations of the two-photon decay rates of highly excited states in hydrogen are compared. The dependence on the principal quantum number (n) of the ns, nd and np initial states is investigated up to n = 100 for the nonresonant emissions. For the ns states together with the main E1E1 channel the contributions of higher multipoles (M1M1, E2E2 and E1M2) are considered. For the np states the E1M1 and E1E2 channels are evaluated. Moreover, the simple analytical formula for the E1M1 decay is derived in the nonrelativistic limit.

One- and two-photon resonant spectroscopy of hydrogen and anti-hydrogen atoms in external electric fields

The resonant spectra of hydrogen and anti-hydrogen atoms in the presence of an external electric field are compared theoretically. It is shown that non-resonant corrections to the transition frequency contain terms linear in the electric field. The existence of these terms does not violate space and time parity and leads to a difference in the resonant spectroscopic measurements for hydrogen and anti-hydrogen atoms in an external electric field. The one-photon 1s–2p and the two-photon 1s–2s resonances are investigated.

QED calculations of three-photon transition probabilities in H-like ions with arbitrary nuclear charge

The quantum electrodynamical theory of the three-photon transitions in hydrogen-like ions is presented. Emission probabilities of various three-photon decay channels for

Theory of the multiphoton cascade transitions with two photon links: comparison of quantum electrodynamical and quantum mechanical approaches

2p_{3/2}

QED model of the radiation escape from matter

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